Process of treating zinc ores.



c. c. TITUS'III w. I. BARENSCHEER.

PROCESS OF TREATING ZINC ORES.

APPLICATION FILED AUG-3|, I914.

ORE

CHLORIDIZER LEACHING VESSEL DISSOVLVED CHLORINE DRYER CHLORIDES OXIDIZEDORE l 0F ZINC PRECIPITATION OF -soDIuI-1 HYPOCHLOR|TE) Fe AND CHLOR'NEcAs T PRECIPITATION 0F zmc ZnCL": NaCL Au. Ag (Pb Cu) H ELECTROLYZEDELECTROLYTIC PRECIPITATION OF ZINC BASIC ZINC CARBQNATE PRECIPITATION 0FCa AND P1 Na CO NmCI, SOLUTION (EvAPoRATEo IF NEcEssARY) 0 NmOH No.61.SOLUTION +NCL I ELECTROLYZED ANODE LIQUOR CH LORINE i run srarns PATENTora ion.

COURT 0. TITUS AND WILLIAM J. BARENSCHEER, OF HELENA, MONTANA, ASSIGNORSTO NEW ENGLAND ELECTED-CHEMICAL METALS COMPANY, OF BOSTON, MASSACHU-SET'I'S, A CORPORATION OF MAINE.

PROCESS OF TREATING ZINC GEES.

Specification of Letters Patent.

Patented Feb. 29, 1916.

Application filed August 31, 1914. Serial No. 859,307.

To all whom it may concern:

Be it known that we, COURT C. TrrUs, and WILLIAM J. BARnNscHEnR,citizens of the United States, residing at Helena, in the county ofLewis and Clark and State of Montana, have invented certain new anduseful Improvements in Processes of Treating Zinc Ores, of which thefollowing is a specification.

This invention relates to cyclic processes for the treatment of ores ofzinc, including concentrates Or tailings from such ores, the processbeing especially adapted for the treatment of complex sulfid orescontaining relatively large proportions of zinc and iron, somemanganese, and variable amounts of gold, silver, arsenic and antimony.Other metals, as lead, copper, cadmium bismuth, calcium and magnesiummay be present in varying proportions. The following is an illustrativeanalysis of a material of this character Insoluble matter 50-55 percent.

together with variable small proportions of arsenic, antimony, bismuthand cadmium.

A preferred embodiment of our cyclic process is as follows, theprincipal steps being illustrated in the accompanying diagrammaticdrawings The dry ore is first chloridized, the metalloids, sulfur,arsenic, and antimony, being eliminated as chlorids, and the basemetals, including zinc, iron, and manganese, and lead and copper ifpresent, converted into soluble chlorids. As such method, we prefer toemploy that described in our prior Patent No. 1,069,498, patented August5, 1913, although we donot desire to be restricted thereto. According tothe said patent, the dry ore is coarsely crushed (to pass a screenhaving eight meshes to the linear inch), mixed with about 5 per cent. of

dry sodium chlorid, and treated with dry chlorin gas, the treatingvessel being externally heated to maintain a temperature above themelting-point of zinc chlorid. Under these conditions the sulfur,arsenic, and antimony are volatilized as chlorids and condensed outsideof the treating vessel. The heavy metal chlorids, with the associatedsodium chlorid serving as a flux, collect in a melted condition in'thevessel and may be tapped out, and thus separated from the gangue. Theseheavy metal chlorids are then brought into solution. As a solvent, wemay use water, or a solution containing sodium chlorid, the latterpreferably derived from the electrolytic cells and containing also somefree chlorin and oXy-chlorin compounds, as below explained.

However the solution may be obtained, it

contains all of the soluble chlorids derived from the ore, together withany sodium chlorid added to the ore or introduced with the leachingsolution. The object of the process, from this point, is ultimately toreplace each of the dissolved metal chlorids by sodium chlorid, themetals being precipitated either as such or in the form of compounds,with the result that the final solution is a commercially pure brine, ofsuch concentration that it may be directly electrolized with economy, orat least may be cheaply evaporated to a suitable concentration forelectrolysis.

With this object in view the acid-reacting solution is first treatedwith a suitable oxyore of zinc, in which term we include the nativecarbonates and silicates of zinc, and also dead-roasted zinc sulfidores, the carbonate and silicate ores being deemed preferable. By thismeans, the iron is precipitated as hydroxid, an equivalent of zincpassing into the solution, which is thereby neutralized. In casemanganese is present, we also add at this stage an equivalent of sodiumhypochlorite, which is produced at a later stage of the process, asexplained below. The efiect of these additions is to eliminate iron andmanganese,'while correspondingly concentrating the zinc and sodiumZhlorids in the solution.

The primary advantage of using nativeoxy-ores of zinc, as compared withchemically-produced zinc oxid or carbonate, hes

in their effect upon the subsequent filtration of the precipitated ironand manganese. These precipitates are, as is well known, colloidal incharacter and diificult to filter; and this character is especiallystrongly marked when the precipitation is effected by means ofchemically-prepared oxy-compounds of zinc. When native ores are used,however, as in the present process, the precipitate is much more easilyremoved by filtration. While the reasons underlying this effect are notcertainly known, it is apparently connected with the slower rate atwhich the precipitation occurs in presence of native ores as comparedwith the chemically-prepared zinc compounds, and also with the physicalnature of the lighter gangue material or insoluble matter of the ore,which passes to the filters with the iron and manganese precipitates.Our preferred practice in handling these precipitates is to agitate thechlorid solution with the native ore, crushed to about 60 mesh, untilthe iron and manganese are completely precipitated; then to decant andfilter the suspendedprecipitate, together with the lighter insolublematerial derived from the ore, the heavier ore-residue being washed outand subsequently treated as its composition may indicate,

Other advantages of using the native ores are their relatively low cost,and the fact that by such use a proportion of the zinc content of suchores is directly extracted and passes into the cycle without the expenseof chloridizing. We have found it practicable to extract as much as 80per cent. of the zinc content of calamin ore by employing it as aprecipitating agent for iron in the manner above indicated.

From the clear solution thus obtained, any gold and silver areprecipitated by means of metallic zinc, with a corresponding slightaugmentation of the zinc chlorid con-- tent of the solution. Lead,copper, cadmium, and bismuth are likewise precip1-' tated if present, atthis stage. In case the orlgmal ore contains considerable proportions oflead, it may be preferable preliminarily to remove the bulk of the leadas chlorid, for example by suitablv cooling the original solution, orotherwise.-

After the precipitation of the precious and associated metals, thesolution consists essentially of the chlorids of zinc and sodium, withsmall proportions of calcium and magnesium chlorid. This solution (or acertain proportion thereof, as hereinafter explained), is now treatedwith normal sodium carbonate, whereby the zinc is completelyprecipitated as basic zinc carbonate, care being taken to avoid so faras possible such excess of sodium carbonate as would also precipitatethe calcium and magnesium. The

I basic zinc carbonate is collected on filters,

and a further small proportion of sodium carbonate is added toprecipitate the calcium and magnesium, the solution being again filteredor decanted.

At this point, we have a more or less concentrated solution consistingessentially of sodium chlorid and water. When the ores have beenchloridized dry in the presence of salt, and the soluble chloridsleached out with a brine solution, as in our preferred process, thisresidual solution usually contains upward of 20 per cent of sodiumchlorid, or a reasonable approximation to saturation. The solution isevaporated if necessary and then electrolyzed in any suitableelectrolytic cell, preferably of the diaphragm type. The direct productsof this electrolysis are chlorin gas; a solution of caustic sodacontaining sodium chlorid; and an overflowing anode-liquor consisting ofnearly saturated brine containing some free chlorin and some oXy-chlorincompounds, such as sodium hypochlorite and chlorate.

, These products re-enter the cycle as follows The bulk of the chloringas is dried (for example by refrigeration), liquefied if desired, andreturned to the chloridizer. quantity of the chlorin gas proportionateto the manganese present in the ore is absorbed in a correspondingquantity of the caustic solution from the cells, and the resultinghypochlorite used for the manganese precipitation as above described.

The bulk of the caustic solution from the electrolytic cells isconverted into normal carbonate by treatment with flue gases, previouslysuitablv purified, and is employed for precipitating the zinc as basiccarbonate,

' as described above.

The chlorinated anode-liquor is led to the leaching vats, and employedfor the extraction of the metal chlorids. In so utilizing theanode-liquor, it is generally necessary to dilute it somewhat, in orderto prevent the precipitation of sodium chlorid in the leaching vessels,through displacement by the more readily solublemetal chlorids of theore. This mode of utilizing the chlorinated anode-liquor is highlyadvantageous, not only because the concentration of the pure sodiumchlorid solution which we ultimately obtain is thereby directlyincreased, but because the free chlorin and oxy-chlorin compounds of theanode-liquor serve to oxidize any ferrous chlorid which may be containedin the chloridized ore. This permits the chloridizing operation to bearrested while someferrous chlorid still remains, thereby economizingchlorin.

consist in precipitating a part only of the zinc as basic carbonate, thebalance being electrolyzed directly, with production of electrolyticzinc and chlorin gas, the latter A modification of the above cycle maypassing through the drying system and thence to the chloridizer. Or anypart 01' all of the zinc-bearing solution from which the precious metalshave been precipitated may be first electrolyzed with insoluble anodesto precipitate a portion of its zinc con.- tent as metal, theimpoverished solution being then treated to precipitate the remainingzinc in the form of basic carbonate, the cycle continuing as abovedescribed.

We claim 1. In a cyclical process plex ores containing zinc,

of treating comthe steps which consist in chloridizing the ore,extracting the soluble chlorids, precipitating the metal contents of thesolution with ultimate replacement of their chlorids by sodium chlorid,electrolyzing the resulting sodium chlorid solution, and applying theevolved chlorin to the treatment of fresh batches of ore entering thecycle.

2. In a cyclical process of treating complex ores containing Zinc, thesteps which consist in chloridizing the dry ore in presence of sodiumchlorid, extracting the soluble chlorids, precipitating the metalcontents of the solution with ultimate replacement of their chlorids bysodium chlorid, electrolyzing the resulting sodium chlorid solution, andapplying the evolved chlorin to the treatment of fresh batches of oreentering the cycle.

3. In. a cyclical process plex ores containing zinc, the steps whichconsist in chloridizing the ore, extracting the soluble chlorids bymeans of a solution containing sodium chlorid, precipitating the metalcontents of the solution with ultimate replacement of their chlorids bysodium chlorid, electrolyzing the resulting sodium chlorid solution, andapplying the evolved chlorin to the treatment of fresh batches of oreentering the cycle.

4:. In a cyclical process of treating complex ores containing zinc, thesteps which consist in chloridizing the ore, extracting the solublechlorids, precipitating the metal contents of the solution with ultimatereplacement of their chlorids by sodium chlorid, electrolyzing theresulting sodium chlorid solution, applying the evolved chlorin to thetreatment of fresh batches of ore entering the cycle, and applying thechlorinated anode liquor as a solvent for the chlorids derived from saidore.

5. In a cyclical process of treating compleX ores containing zinc, thesteps which of treating comconsist in chloridizing the dry ore inpresence of sodium chlorid, extracting the soluble chlorids,precipitating the metal contents of the solution with ultimatereplacement of their chlorids by sodium chlorid, electrolyzing theresulting sodium chlorid solution, applying the evolved chlorin to thetreatment of fresh batches of ore enterchlorids derived from said ore,and carbomating the caustic product of the electrolysis and utilizingthe same for the precipitatlon of zinc.

7. In a cyclical process of treating complex ores containing zinc, thesteps which consist in chloridizing the dry ore in pres ence of sodiumchlorid, extracting the soluble chlorids, precipitating the metal contents of the solution with ultimate replacement of their chlorids bysodium chlorid, electrolyzing the resulting sodium chlorid solution,applying the evolved chlorin to the treatment of fresh batches of oreentering the cycle, applying the chlorinated anodeliquor as a solventfor the chlorids derived from said ore, and carbonating the causticproduct of the electrolvsis and utilizing the same for theprecipitationof zinc.

8. The hereindescribed cyclic process of treating sulfid ores containingzinc and iron, which consists in chloridizing the ore, extracting thesoluble chlorids, precipitating the iron by means of an oXy-ore of zinc,thereby concentrating the zinc content of the solution, precipitatingzinc by means of sodium carbonate, thereby concentrating the sodiumchlorid content of the solution, electrolyzing the resulting so liumchlorin solution, applying the evolved chlorin to the treatment of freshbatches of ore entering the cvcle, and carbonating the caustic productof the electrolysis and utilizing the same for the precipitation ofzinc.

9. The hereindescribed cyclic process of treating sulfid ores containingzinc and iron, which consists in chloridizing the ore, extracting thesoluble chlorids,precipitating the iron by means of an oXy-ore of zinc,thereby concentrating the zinc content of the solution, precipitatingzinc by means of sodium carbonate, thereby concentrating the sodiumchlorid content of the solution, electrolyzing the resulting sodiumchlorin so-- 10. The hereindescribed cyclic process of treating sulfidores containing zlnc, iron, and manganese, which conslsts in Ichloridizing the ore, extracting the solubonating the caustic product ofthe electrolysis and utilizing the same for the precipitation of zinc.

In testimony whereof, we afiix of signatures in presence of twowitnesses.

COURT 0. TITUS. WILLIAM J. BARENSCHEER.

Witnesses to the signature of Barenscheer:

ALBERT J. GALEN, PEARL YOUNG. Witnesses to the signature of Court C.Titus:

MORRIS SCI-INEEDE, M. L. HEWETT.

